Do not forget to read the thread on How to upgrade firmwarehttp://www.mobileread.com/forums/showthread.php?t=62973
... and do not forget to backup your installed dictionaries, themes, fonts, translations, applications, logos, notes, books and whatever else you might have on your reader. Better safe than sorry ;-)

The built-in "unzipper" in Windows doesn't like it, and neither does my rather old version of WinRAR. Looks like it's time to upgrade to the latest version of WinRAR - it can (according to the website) handle ".7z" archives, as fjtorres confirms.

Could you try to persuade PB to re-upload them as ZIP files? It would make life a LOT easier for people .

It's not a problem for "techies" like us. It's "Joe Public" who's going to have a significant issue with this. It seems madness to release a firmware upgrade in an obscure compression format that the popular operating systems can't handle natively.